it is possible to concatenate one result set onto another in a single query? - postgresql

I have a table of Verticals which have names, except one of them is called 'Other'. My task is to return a list of all Verticals, sorted in alpha order, except with 'Other' at the end. I have done it with two queries, like this:
String sqlMost = "SELECT * from core.verticals WHERE name != 'Other' order by name";
String sqlOther = "SELECT * from core.verticals WHERE name = 'Other'";
and then appended the second result in my code. Is there a way to do this in a single query, without modifying the table? I tried using UNION
(select * from core.verticals where name != 'Other' order by name)
UNION (select * from core.verticals where name = 'Other');
but the result was not ordered at all. I don't think the second query is going to hurt my execution time all that much, but I'm kind of curious if nothing else.


UNION ALL is the usual way to request a simple concatenation; without ALL an implicit DISTINCT is applied to the combined results, which often causes a sort. However, UNION ALL isn't required to preserve the order of the individual sub-results as a simple concatenation would; you'd need to ORDER the overall UNION ALL expression to lock down the order.
Another option would be to compute an integer order-override column like CASE WHEN name = 'Other' THEN 2 ELSE 1 END, and ORDER BY that column followed by name, avoiding the UNION entirely.

Related

Use postgresql query results to form another query

I am trying to select from one table using the select result from another table. I can run this in two queries but would like to optimize it into just one.
First query.. Select ids where matching other id
select id from lookuptable where paid = '547'
This results in something like this
6316352
6316353
6318409
6318410
6320468
6320469
6320470
6322526
6322527
6324586
6324587
6326648
I would like to then use this result to make another selection. I can do it manually like below. Note, there could be many rows with these values so I've been using a IN statement
select * from "othertable" where id in (6316352,6316353,6318409,6318410,6320468,6320469,6320470,6322526,6322527,6324586,6324587,6326648);

select
ot.*
from
"othertable" as ot
join
lookuptable as lt
on
ot.id = lt.id
where
lt.paid = '547'

The IN operator supports not just value lists but also subqueries, so you can literally write
select * from "othertable" where id in (select id from lookuptable where paid = '547');

Single Value Expression in When Then Aggregate Function TSQL

I am trying to map a certain value of a column based on its count on another table. If the count of [Location] i.e a column of IMPORT.DATA_SCRAP table in each row. For now for location static value i.e Utah and Kathmandu is supplied for test purpose only is equal to 1, then only i need to get the result in the select statement i.e only single value expression must be returned but here n rows of table with value is returned.
For. eg. In the below query,total rows of IMPORT.DATA_SCRAP gets returned, i only need the single first row value in my case.
I came to know whether cursor or CTE will acheive my result but i am unable to figure it out.
Here,
select
case
when
((SELECT COUNT(stateName) FROM Location.tblState where stateName = 'Utah')=1)
then (select stateName, CountryName from Location.tblState where stateName= 'Utah')
end as nameof
from IMPORT.DATA_SCRAP
The relation between country, state, city is as below:
select
case
when
((SELECT COUNT(cityName) FROM Location.tblCity where cityName = 'Kathmandu')=1)
then (select ct.countryName from Location.tblCity c
inner join Location.tblState s
on c.stateID = s.StateID
inner join Location.tblCountry ct
on ct.countryId = s.CountryId
where c.cityName = 'Kathmandu'
)
end as nameof
from IMPORT.DATA_SCRAP
How can i return only a single value expresion despite of multiple nmax rows of IMPORT.DATA_SCRAP row in the result.
If i comment out the -- from IMPORT.DATA_SCRAP in the above query i would get the desired single result expression in my case, but unable how can i acheive it in other ways or suggest me the appropriate way to do these types of situation.

Querying part of a string

I am trying to query a column which contains string such as
595.1,N30.10
630.5,E10
I have tried separating the two values into different columns
split_part(code, ',', 1) AS code1,
split_part(code, ',', 2) AS code2
But now I see that some of the rows have 3 (or could be more)
785.59, R57.1, R
I wonder if there is a way to specify and query only the first part of the string without having to split the string. In this case only look for enteries with 595.1,785.59 and ignore the rest.
SELECT distinct ON (id) id,time,year,code
FROM data
where code= ANY('{595.1,785.59}');

I think you already the have logic you need, you only need to thread it together:
SELECT DISTINCT ON (id) id, time, year, code
FROM data
WHERE split_part(code, ',', 1) = ANY('{595.1,785.59}');
This logic appears to be working in the demo below.
Demo

To query on first part of code column you can do like below
SELECT * FROM tableName
WHERE split_part(code, ',', 1) = somevalue

oracle: grouping on merged columns

I have a 2 tables FIRST
id,rl_no,adm_date,fees
1,123456,14-11-10,100
2,987654,10-11-12,30
3,4343,14-11-17,20
and SECOND
id,rollno,fare,type
1,123456,20,bs
5,634452,1000,bs
3,123456,900,bs
4,123456,700,bs
My requirement is twofold,
1, i first need to get all columns from both tables with common rl_no. So i used:
SELECT a.ID,a.rl_no,a.adm_date,a.fees,b.rollno,b.fare,b.type FROM FIRST a
INNER JOIN
SECOND b ON a.rl_no = b.rollno
The output is like this:
id,rl_no,adm_date,fees,rollno,fare,type
1,123456,14-11-10,100,123456,20,bs
1,123456,10-11-12,100,123456,900,bs
1,123456,14-11-17,100,123456,700,bs
2,Next i wanted to get the sum(fare) of those rollno that were common between the 2 tables and also whose fare >= fees from FIRST table group by rollno and id.
My query is:
SELECT x.ID,x.rl_no,,x.adm_date,x.fees,x.rollno,x.type,sum(x.fare) as "fare" from (SELECT a.ID,a.rl_no,a.adm_date,a.fees,b.rollno,b.fare,b.type FROM FIRST a
INNER JOIN
SECOND b ON a.rl_no = b.rollno) x, FIRST y
WHERE x.rollno = y.rl_no AND x.fare >= y.fees AND x.type IS NOT NULL GROUP BY x.rollno,x.ID ;
But this is throwing in exceptions.
ORA-00979: not a GROUP BY expression
00979. 00000 - "not a GROUP BY expression"
The expected output will be like this:
id,rollno,adm_date,fare,type
1,123456,14-11-10,1620,bs
So could someone care to show an oracle newbie what i'm doing wrong here?

It looks like there's a couple different problems here;
Firstly, you're trying to group by an x.ID column which doesn't exist; it looks like you'll want to add ID to the selected columns in your sub-query.
Secondly, when aggregating with GROUP BY, all selected columns need to be either listed in the GROUP BY statement or aggregated. If you're grouping by rollno and ID, what do you want to have happen to all the extra values for adm_date, fees, and type? Are those always going to be the same for each distinct rollno and ID pair?
If so, simply add them to the GROUP BY statement, ie,
GROUP BY adm_date, fees, type, rollno, ID
If not, you'll need to work out exactly how you want to select which one to be output; If you've got output like your example (adding in an ID column here)
ID,adm_date,fees,rollno,fare,type
1,14-11-10,100,123456,20,bs
1,10-11-12,100,123456,900,bs
1,14-11-17,100,123456,700,bs
Call that result set 'a'. If I run;
SELECT a.ID, a.rollno, SUM(a.fare) as total_fare
FROM a
GROUP BY a.ID, a.rollno
Then the result will be a single row;
ID,rollno,total_fare
1,123456,1620
So, if you also select the adm_date, fees, and type columns, oracle has no idea what you mean to do with them. You're not using them for grouping, and you're not telling oracle how you want to pick which one to use.
You could do something like
SELECT a.ID,
FIRST(a.adm_date) as first_adm_date,
FIRST(a.fees) as first_fees,
a.rollno,
SUM(a.fare) as total_fare,
FIRST(a.type) as first_type
FROM a
GROUP BY a.ID, a.rollno
Which would give the result;
ID,first_adm_date,first_fees,rollno,total_fare,first_type
1,14-11-10,100,123456,1620,bs
I'm not sure if that's what you mean to do though.

Select from any of multiple values from a Postgres field

I've got a table that resembles the following:
WORD WEIGHT WORDTYPE
a 0.3 common
the 0.3 common
gray 1.2 colors
steeple 2 object
I need to pull the weights for several different words out of the database at once. I could do:
SELECT * FROM word_weight WHERE WORD = 'a' OR WORD = 'steeple' OR WORD='the';
but it feels ugly and the code to generate the query is obnoxious. I'm hoping that there's a way I can do something like (pseudocode):
SELECT * FROM word_weight WHERE WORD = 'a','the';

You are describing the functionality of the in clause.
select * from word_weight where word in ('a', 'steeple', 'the');

If you want to pass the whole list in a single parameter, use array datatype:
SELECT *
FROM word_weight
WHERE word = ANY('{a,steeple,the}'); -- or ANY('{a,steeple,the}'::TEXT[]) to make explicit array conversion

If you are not sure about the value and even not sure whether the field will be an empty string or even null then,
.where("column_1 ILIKE ANY(ARRAY['','%abc%','%xyz%']) OR column_1 IS NULL")
Above query will cover all possibility.